CT Scans

This is a lengthy and detailed review of a complicated subject, full of excellent references, representing the extensive research and the strong and well reasoned opinions of the writer, Wayne Wells AKA WWW. WWW is a well respected contributer to CLL patient forums. The reader may want to chew off only one or two parts at each reading.

The Question of CT Scans – Be Informed

Out of my experiences in the trenches of Wait & Watch or Wait & Worry (W&W), conventional therapy and clinical trials, my agenda will be to convince you that there is both an excessive use of CT scanning and a need to better define reasons for use of scanning in CLL. Excessive and unnecessary scans are unacceptable because ionizing radiation is potentially harmful and it is cumulative. My message recognizes that CT scanning is an important tool and a requirement for enrollment in promising clinical trials. As an informed patient, however, you might have room to substantially diminish your exposure to ionizing radiation.

After exploring the subject of CT scanning I realized early on that the subject would be difficult, controversial and prone to misunderstandings. In the simplest of terms, I want YOU, as a patient or caregiver, to feel the need to be an integral participant in the decision process of when to allow a CT scan. You need to be educated to be an effective advocate.

PART I

Foundation For Concern

CT scans are but one of the most common diagnostic tools that use ionizing radiation to see inside our bodies to locate tumor tissue or lymph nodes that can then be measured to assess danger or monitor effects from therapies. Ionizing radiation damage to cellular DNA is the risk side of CT scanning since ionizing radiation is quite good at breaking chemical bonds (radiolysis) in cells. If you can envision the double helix of our DNA, a twisted ladder-like structure, it contains all the coded information we need to keep reproducing cells that are healthy and functioning properly. Ionizing radiation will cause single- and double-stranded breaks of the DNA in genes that are usually either repaired or given signals to die (apoptosis) if they are not repairable. Double- stranded breaks in our DNA are particularly hard to repair and we are dependent on healthy immune system functions for those damaged cells to be repaired properly or destroyed. When one has a cancer of the immune system like CLL, and when we are often subjected to treatments that further suppress or increase the damage to immune function, the resulting amount of damaged cells that are not properly repaired or fail to obey signal commands to commit apoptosis will reproduce imperfectly to become oncogenes that can eventually evolve into cancers.

I believe there is a need for all of us, as a community, to bring pressure on the powers- that-be to reduce radiation exposure through an examination of how the system is currently run and what we might experience in the way of radiation exposure on our respective CLL journeys.

Everything Needs Context

But aren’t we living with ionizing radiation all the time? So what’s the big deal? Correct, the average yearly exposure of a U.S. resident is 3 to 3.2 mSv (millisievert). SI or sievert is the unit of effective dose measurement. For the curious, an in depth discussion can be found here. Remember, ionizing radiation damage to our tissues is cumulative.

I will break down our examination of CT use into two contextual arenas with the first arena having “a” and “b” parts:

1a) the clinical management of CLL during the W&W phase, and

1b) throughout the standard treatment phase, separate from:

2) the clinical trial phase.

Looking at CT use in the first context of W&W and also during standard therapy, YOU, as the patient or caregiver, must be proactive in being an integral part of the decision to allow CT scanning! Don’t accept the order for a CT scan without justification criteria that makes sense to you. Asking appropriate questions and assessing the validity of the answers to your “informed” satisfaction will reduce unnecessary scanning. CTs cannot diagnose CLL and are not required. Sadly, doctor ignorance of CLL and possibly fear of litigation are probable drivers for much over-scanning. Your polite refusal, if not satisfied for the reason behind being scanned, may be all the doctor needs to protect him or herself.

In the second contextual arena, a clinical trial may be in your future. Clinical trials are becoming more attractive with greater benefit vs risk, and are a necessity for many patients who have run out of therapy options. Clinical trials, however, will mandate a series of CT scans as part of trial protocol. This fact highlights the significance of prior radiation exposure received in the W&W stage, or during standard treatment since ionizing radiation is cumulative. Clinical trial participation and CT scanning cannot be mutually exclusive.

In addition, your age matters. Your sex matters. You should be acutely aware that the younger you are, and if you are female, the more you need to question your risk vs benefit from CT scanning in the clinical management phase of W&W, and to a lesser degree, in the standard treatment phase.

PART II

A Bit About CT Scanners

CT means “Computerized Tomography” and is the same as a CAT scan or “Computerized Axial Tomography” scan. There is some indication that there is a place for FDG-PET (Fludeoxyglucose Positron Emission Tomography) scans with some CLL patients showing indications of potential Richter’s Transformation. For more information, click here.

CT scanners are produced by many companies and the technology is rapidly changing. A quick review of manufacturers lists GE with nine models, Siemens with nine, Philips with seven and Toshiba with seven. Model names actually can hint at a lower radiation dose machine if it has the word “dual” in it. CT scanners cost big bucks, however, and many older machines work well so they are kept in service, delivering much higher doses of ionizing radiation than the newest models. Do you know how old the machine is that you will be scanned on? Ask. Software updates for older machines can reduce radiation exposure but not all older machines can be successfully retrofitted. Ask about that.

Relying on CT scan technicians and technical literature, the range of radiation, in terms of “chest X-Rays,” can vary from 30 to 450 per scan! If you are about to be scanned, which machine would you opt for? The CT that will give you 450 chest X-rays per scan will not deliver better information than the CT that delivers 30 chest X-rays of ionizing radiation. Any machine described as a dual source machine will give some confidence that you are in the lower ranges of radiation exposure. On larger medical campuses you may have a choice of newer/better vs older/worse CT scanners. Ask.

Why Don’t We Just Trust Our Doc’s Judgment?

Why should the CLL patient not just follow the doctor’s judgment to get a CT when ordered? There is admittedly a gray area in arguing the question of need for CT scanning from any one given patient’s situation. Since you, the patient, with skin literally in the game, or caregiver, to be intelligently engaged as part of the decision process of whether or not to allow a CT scan, I offer these observations:

Too often I read patient postings that suggest unwarranted use of CT scans, most often right at the time of diagnosis and during a patient’s period of W&W. This may be more prevalent in societies that have a pay-per-service healthcare system, such as the U.S., but I suspect overuse of CT scanning is most prevalent among doctors unfamiliar with CLL/SLL regardless of where in the world they might be. When you were diagnosed how many of you were sent to be CT scanned right away? How many of you asked the questions “Why is this necessary?” and “How will what you see help you guide my care?” I had this happen to me, and no, I did not ask these questions at first. CT scanning is not required for diagnosis of CLL.CT scans are not therapeutic. General oncologists who see few CLL/SLL patients in his/her practice will likely order additional unnecessary CT scans during W&W not considering the utility of ultrasound and MRI scanning which do not use ionizing radiation.

Richter’s Transformation (RT or RS) is a dreadful but infrequent (~5 to 10%) complication of CLL that becomes a fast-growing and often deadly Diffuse Large B Cell Lymphoma (DLBCL) that is best caught early. So is this a rationale for early or frequent CT scans for all CLL patients?Since RT can appear suddenly and is a rapid growth lymphoma, one needs to ask this question of their oncologist: “How frequently would a patient need to be scanned for an early warning of Richter’s?” A CT scan cannot differentiate early RT from SLL. In the case of SLL where CLL cells manifest primarily in the lymph nodes, a CT scan is useless to distinguish between SLL, MZL or MCL which requires biopsy and molecular diagnosis. You can read more about this here and here.

There is a scanning case to be made when there is the discovery of markers that suggests a patient may transform to the dreaded Richter’s (DLBCL)—2p gain, TP53, NOTCH1 activation, and disruption of CDKN2A/B—along with rapid node growth and rising lactate dehydrogenase (LDH). The FDG-PET scan has use in locating optimal node location for biopsy. You can read more about it here and here, but please note FDG-PET limitations.

Clearly, the CT scan is a useful tool but needs to be used judiciously and appropriately. If your doctor offers you a convincing reason for a CT scan, then go for it. Just don’t passively accept it because it is ordered for you without being given a convincing reason. Challenge a reason such as “We need to see the internal nodes that can’t be felt or seen” as to its clinical usefulness. The younger you are when diagnosed, the more likely you are to have more CT scans ordered and thereby accumulate more radiation-damaged DNA while dancing with the CLL Bear. Make ’em count! Are you unsure whether to follow your doctor’s orders to get a scan? Then ask for a second opinion from a CLL expert if at all possible.

PART III

Who Is Claiming CT Overuse Besides Me?

In an additional nod to the contrarian warnings over CT overuse, here is a paper that dismisses the concern. You read. You decide. But as you read, I hope you are comparing it to the other warning opinions while keeping in mind that our CLL community, by definition, is less capable at repairing damaged DNA and NONE OF THESE PAPERS, PRO OR CON, DISCUSSES CT USE IN THE SPECIFIC CONTEXT OF CLINICAL TRIAL DATA ACQUISITION WHERE FREQUENT CT SCANS ARE REQUIRED.

As I previously mentioned, there is support IN SOME CASES for scanning CLL/SLL patients with specific clinical signs, and/or the presence of markers on tested blood. The scan in question is the FDG-PET and not the CT scan. It should be noted that findings indicated patients with aggressive CLL (HAC) and Richter’s both had high standardized uptake values (SUV). SUV refers to a cancer cell’s metabolic rate to bring in more or less radioactive sugar that the patient gets through an IV. Rapidly growing tumor cells (Richter’s and HAC) use much more than what slower growing CLL cells would do in indolent CLL (HIC). The paper clearly states that tissue biopsy is preferred for diagnosis of Richter’s. It is the utility of the FDG-PET in selecting the best tissue for biopsy. This is not something best left up to the general oncologist who knows less than the average bear about CLL and Richter’s. Nodes that are transformed to Richter’s are often internal and Fine Needle Aspiration (FNA) too often gives false negatives. The FDG-PET can select the most promising tissue mass to do a core biopsy. The message I take is that CTs won’t be useful, but in the presence of histological evidence and clinical observations, an FDG-PET is most appropriate; just don’t put the cart before the horse.

Currently, some U.S. states are adopting CT radiation regulations over concerns of potential harm. If you are treated in the U.S., check this site and see if your state is, or has, enacted legislation. If you are outside the U.S., click and compare to your country’s policy.

Authoritative Viewpoints

On the cautionary front, in his book One Doctor, Professor Brendan Reilly, MD of Weill Medical College writes: “Seventy million CT scans are performed annually in the United States—all of them expensive and many of them unnecessary. (Worse, it is estimated that ionizing radiation from these CT scans will cause fifteen thousand to thirty thousand cancers annually—1 to 2 percent of all new cancers diagnosed.)” This is a general assessment, so expect the percent of CT-caused cancers to be higher in our younger community members already prone to developing secondary cancers in the absence of any CT scanning. This fact should be a wake-up call especially for women. Women, in general, live longer than men and a woman who is 65 can reasonably expect to make it to 85 in the oft-touted 20-year time frame for a possible secondary cancer to show its ugly self. As treatments promise longer overall survival (OS), does this not, in itself, argue for heightened discretionary CT use in patients under 65? The younger you are, the more you should be wary.

Since the 2009 Lymphoma Research Foundation (LRF) Conference in Brooklyn NY, oncologist lecturers have been spreading the message that CT scans are being over used. At the 2013 LRF Conference, Dr. Matthew Davids of Harvard Medical School and Dana Farber Institute, and Dr. Kieron Dunleavy of the National Cancer Institute, as part of their formal presentations, sent the message out discouraging the need for CT scanning in CLL.

From the American Association of Physicists in Medicine (AAPM) 2008 Report 96 on Effective Dose for Ionizing Radiation: “It is important to recognize that the potential biological effects from radiation depend not only on the radiation dose to a tissue or organ but also on the biological sensitivity of the tissue or organ irradiated.”

On top of everything else, due to human and technology error one cannot rule out getting improper dosages of radiation: Read the article here.

PART IV

More On The Need For CT Scanning

Most patients initially diagnosed with CLL are in a state of anxiety and perhaps the CT scan is a surrogate for “doing something” in the land of W&W with feel-good benefits extending to the doctor as well as the patient. This is not a smart or beneficial rationale for patient exposure to ionizing radiation.

Need an even better reason to avoid excessive CT scans early in W&W? You are increasingly a potential candidate to take part in some future clinical trial which will demand CT scans as a condition of your enrollment.

Consideration for future participation in a clinical trial should be held in your mind as an all-important context where frequent CT scans will be required as opposed to the clinical management context of CLL in W&W, or even the therapy context of your CLL journey. I would urge everyone to adopt the mindset that they will be actively seeking enrollment in a clinical trial at some time in future. The newer agents and understanding of CLL biology will almost guarantee benefits for quality of life, and longevity with less side effects, not to leave out your contribution toward new and better ways to treat all the members of our Tribe. All of those positives will be gained only through acceptance of multiple CT scans.

Certain clinical symptoms such as pain, organ dysfunction or histologically discovered makers may require imaging to see what is going on. You may sense something your doctor might be missing that warrants you asking for a CT scan—but ask if an ultrasound image or an MRI would suffice. Neither technology involves use of ionizing radiation. Payment for MRIs, or patients with pacemakers, may be problematic, so check with your insurance. I had a pacemaker implant in 2012 that is MRI tolerant so keep that in mind if a pacemaker is in your future.

A wise family doctor suggested an ultrasound as opposed to my first NY oncologist who ordered a CT to see if internal nodes were obstructing kidney function due to unexplained and worrying test results early in W&W showing rising creatinine and decreasing kidney filtration—a valid situation for imaging need. An ultrasound worked well for me in that case.

After completing a therapy protocol it makes sense to assess the efficacy of the treatment on the internal nodes by CT to strategize the need for stopping or continuing therapy. We should not be universally for or against CT scans. “Know when to hold ’em Know when to fold ’em,” as an old poker player might sing. Play your hand well.

PART V

Clinical Trial CT Scan Context

There is solid rationale for CT scanning in a clinical trial setting that cannot be avoided, but is it adequate or overkill? Who decides?

There are so many newer drugs that promise better efficacy with less toxicity that it is hard to keep up with them. All these drugs will require clinical trials that must produce evidence of efficacy and safety. Ibrutinib and Idelalisib are two drugs that illustrate the difficulty of obtaining that evidence. These two drugs initially cause an increase of cancer cells in the peripheral blood, unlike standard chemo and monoclonal antibodies (mAbs) that show an immediate decrease as the cells are killed off.

Many lymph nodes are not visually observed or felt by palpation but can be used as evidence of efficacy if objectively measured to prove reduction of the total tumor burden, even while Absolute Lymphocyte Count (ACL) is on the rise. Objective measurement of lymph nodes via CT scanning is necessary for the drug developer to convince the FDA of a drug’s efficacy, which will lead to drug approval by the FDA.

Recently I made contact with a National Cancer Institute (NCI) researcher who provided a number of insights. I asked who is responsible for setting the criteria that involves CT scans for the evidence of drug efficacy and safety that will be required for FDA approval. He explained that the gold standard for drug approval is Overall Survival (OS) and in the absence of that there are surrogate endpoints. I remember Dr. Byrd musing on the dilemma of quantifying the “feeling great” reaction of so many Ibrutinib patients soon after taking the drug in the early trials. Is patient subjective reaction regarding quality of life a valid endpoint? Whether patient subjective feelings will ever be considered as endpoints is debatable but node reduction in spite of Absolute Lymphocyte Count (ACL) rise is a legitimate and objective endpoint via CT imaging.

The Kinase Inhibitors (KIs) Ibrutinib and Idelalisib have made endpoint evaluation an important goal for FDA approval and may be a major factor behind frequent CT use. I am still working on who is setting the CT use agenda and what is really necessary as opposed to what is being done. Questions I have not received adequate answers for revolve around who decides how many scans a clinical trial “lab rat” will get and is there a patient advocate perspective in the decision process? Even if frequent scans are deemed necessary, is anyone setting out guidelines for institutions conducting clinical trials assuring that “lab rats” like you and me are getting those scans on the lowest radiation dose machines?

A personal story illustrating my concerns occurred during the recent Needham, MA Lymphoma Research Foundation (LRF) Conference: one of the two Dana Farber oncologists giving a formal presentation gave the now familiar nudge to the audience on participating in clinical trials and the also familiar warning of inappropriate CT scanning. Both subjects I had planned to ask questions about. At questions from the audience, I emphasized the doctor’s push for clinical trial participation by describing my experience with PCI-32765 (Ibrutinib) and finished up by saying I wished to pick up on an issue related to unnecessary CT scanning in the clinical trial context. I said I had not been treated at Dana Farber and since I assumed that he was involved in clinical trials, what was Dana Farber, as an institution, or he as an investigator, doing to minimize ionizing radiation to clinical trial patients and what could he tell the audience about CT machines used at Dana Farber that use low-dose radiation technology.

His reaction was to look down at his watch in an uncomfortably long pause and finally blurt out “I don’t know what machines are used but if you have a problem with radiation exposure you should take it up with the pharmaceutical company. Next question.”

I don’t know about you, but at that point I no longer had a problem with just radiation exposure but a problem with who is looking out for the patients who are being asked to endure frequent scanning.

For the record, I volunteered for the National Institutes of Health (NIH) Natural History Study in which I knew I would be scanned. And, this was at a time in which I had a record of scan refusal by local oncologist recommendation. I believe in the progress of advancing medical breakthroughs by trial participation but I want to know somebody has our back on safety issues. That Dana Farber doctor did not inspire confidence that clinical trial patients were indeed anything more than “lab rats.”

PART VI

Inside The “Donut” – How Many Scans?

When a CT scan is ordered for you, think of it as a “session” because unless you ask, you won’t know how many actual scans you are getting. A typical CT session may be one, two or three scans. In certain machines you will be as a loaf of bread being “sliced” by bursts of radiation where each slice is typically 5mm thick. There are also machines that employ a spiral use of radiation to generate the required images. These may be referred to as helical CTs and are newer and faster but do not necessarily use less radiation than other non-helical machine designs. There are also single- and dual-source configured machines (referring to the number of places in the scanner the radiation is projected).

The key to lowest dose radiation exposure is not in the hardware but in the software used for reconstructing the data into the final image. Dual-source machines and helical CTs are newer and can be assumed to operate with low-dose software, but some single-source CTs can also operate with low-dose software. Older machines may or may not have the capability to be upgraded for use with low-dose software. You need to question this.

Ionizing radiation exposure for you will be determined by your body size and weight and what tissue is actually scanned. A scan of just your head/neck will not require as much radiation as other softer tissues.

From the 2008 American Association of Physicists in Medicine (AAPM) report 96 – 3.8 Effective Dose (E): “A 100-mGy dose to an extremity would not have the same potential biological effect (detriment) as a 100-mGy dose to the pelvis35.” In section 4.4 Size-or Weight-Based Technique Charts: “…the normalized nature of CT data (i.e., CT numbers represent a fixed amount of attenuation relative to water) ensures that the image always appears properly exposed. As a consequence, CT users are not technically compelled to decrease the tube-current-time product (mAs) [milliamperes] for small patients, which may result in excess radiation dose for these patients. It is, however, a fundamental responsibility of the CT operator to take patient size into account when selecting the parameters that affect radiation dose, the most basic of which is the mAs.12, 14”

Each clinical trial CT scanning session may typically be three CT scans with two overlapping areas of tissue comprising the Aortal Arch and Upper Lung tissue which lies between the head/neck scan and the chest scan. Scanning overlap of kidney/liver organs lies between the chest scan and the pelvic/abdominal scan. Both overlapping tissue areas will receive, on the older machines with higher radiation dosing, between 600 and 900 chest X-rays of radiation. OK, so how many scan sessions can the clinical trial patient expect to have in the course of a trial? Because some of the sessions may only be one scan with no tissue overlap or two scans with one tissue overlap, that number is hard to answer precisely but I will provide a real life example with some hypothetical variation dependent on model of CT scanner and software used in image reconstruction.

Radiation Risk Video And Calculator

I have been searching for simplified ways to express to you the risk from CT scanning without getting overly technical. Remember, the younger you are, and if you are female, the risk goes up—particularly using the age criteria. One of the many questions for which I have not been able to obtain a convincing answer is whether an immune deficient CLL patient is at greater risk from the same amount of ionizing radiation than an equivalently aged healthy immune person? Simplistic logic would seem to suggest there is a greater risk in immune compromised people.

You can click here for a very cool X-ray risk calculator. I would suggest playing around with it by putting in information such as a 40-year-old female vs a 70-year-old man to impress upon you where the risk is gravest.

Suggestions for use: Remember to click on the menu for scan type, i.e. “plain film X-ray” (default) vs “CT scan” (select each time you change data input). Then select body tissue or area of scan and the calculator will put in a millisievert (mSv) value for you. This will likely not be what your actual scans expose you to but it can be a way to calculate relative risk given age and gender. You might want to put in an arbitrary number of scans that are likely in a clinical trial scenario for one year, even if you are in the W&W stage of your CLL journey. I suggest four or five scans. Since radiation is cumulative, throw in ten scans and see what you get. The calculator is cool in that it gives some other risk data at the bottom to put “risk” in a perspective of sorts. If you keep a log of your radiation exposure from all sources you could easily tailor this calculator to be more specific and accurate for you and your individual scanning experiences.

Two Important Professional Perspectives With A Scary Revelation

We patients need to be involved in our scanning experience to sharpen the attention paid to whomever should be looking after our safety and well-being. Thank the powers-that-be that I am not alone in raising concern over CT scanning risks as I present another short read with a link to a scary bit of history involving CT diagnostically harmed patients. I knew of therapeutic radiation harming patients but had not appreciated the risk of radiation overdose from diagnostic CTs until I came on this short read from the American Association of Physicists in Medicine (AAPM). When reading the short AAPM article, click on the blue link that begins “and several unfortunate cases ….”

The alarm has been duly raised and acted on in the context of pediatric CT scanning. This is appropriate. And, while it is basically true that CLL is diagnosed primarily in folks over age 65 where a likely cancer from CT scanning will not occur until 10 to 20 years later, what about our younger members? While it is rare, but possible, for CLLers to get three, four and five secondary cancers, it begs the question of whether our patient population is more at risk for developing a secondary cancer from CT radiation and getting it sooner due to basic immune deficiencies.

The National Electrical Manufacturers Association (NEMA) has created a standard for alerting CT operators to a potential radiation overdose before the patient is actually scanned. This is referred to as “NEMA XR 25 Computed Tomography Dose Check.”

When you get your next CT scan, does the CT scanner operate with this standard? Are you going to ask if it does? The overdose cases in the video are a small number of patients in the overall number of patients scanned every year so it is unlikely you will have this happen to you. If you voice your concern to your doctors and CT operators you are helping to ensure this will not happen to anyone in the future.

PART VII

So, You Are About To Be CT Scanned

Here are several important perspectives regarding CT scanning that need to be considered in a personal context on your unique CLL journey. It has been a universal medical consensus that CT scanning has been over prescribed even though CTs are universally acknowledged as important diagnostic tools. The potential for CT scans increasing odds of contracting other cancers is very real in a pediatric setting. The risk of secondary cancers in adults has many variables but is largely time dependent (generally thought to require about 20 years), generated from radiation-damaged DNA that does not get properly repaired. If you are 70+, the odds of a secondary cancer from CT radiation is not the same as if you are in your 30s.

One way of assessing CT risk is to evaluate the research data on population exposure. One subset of the population, well studied were women undergoing annual mammography. A radiology physicist I recently spoke with said there was no statistically elevated risk of cancer from mammography on the radiation-sensitive organ of the breast. In the female CLL population, however, in which a woman might have a history of mammography exposing her to cumulative radiation, which is then added to by frequent CTs, will the risks not be increased? Does this play equally well within the CLL population undergoing multiple CT scans every few months while in a clinical trial? Since all cancer is, in a sense, a failure of immune function, and CLL is fundamentally a cancer of immune function in which the second greatest cause of death is secondary cancers, I would say the jury is out in the absence of a CLL frequently scanned population study.

CT scans are going to be a greater part of the patient experience in a clinical trial setting due to exciting new drugs offering the promise of greater efficacy and less side effects. Avoiding these clinical trials because of fears over ionizing radiation exposure will become less if we patients help in the effort to usher in the use of newer scanning software that will guarantee minimal radiation exposure and host overdose warning features before we get “nuked”.

Generic CT Scan Assessment

What can you, the patient, do to find out if your medical facility is complying with the highest standards for CT scan radiation dose reduction and safety?

Virtually all U.S. facilities may report use of “low-dose” software. All CT machines now manufactured and sold in the U.S. are of the helical design and capable of supporting the latest version of low-dose software. Older CT scanners and earlier versions of software remain problematic at some institutions and I will almost guarantee that your doctor will not know or admit to knowing the status of CT technology at his/her institution. This is due in part to the number and variety of machines. As one example, at Ohio State University (OSU) Medical Center they currently have 14 CT scanners, expected to increase to a total of 17 in the near future.

The term “low-dose” is not specific enough and various CT manufacturers are continually leapfrogging better machines into the market. Therefore, I cannot recommend a specific machine. “The soul is in the software” and I believe I have reduced the low-dose and safety issues to four questions you will want answered in the affirmative the next time you are scanned. Ask the following of your scheduling contact:

Does the CT scanner use iterative image reconstruction software?

Does the CT scanner I will be scanned on have kV modulation? kV stands for kilovolt.

Does the CT scanner I will be scanned on have mA modulation? The mA stands for milliampere. Note: One of the basic parameters affecting radiation dose for a smaller patient is in the hands of the CT operator adjusting mAs. For those who have a need to know more about kV and mA, check here.

Does the CT scanner I will be scanned on have organ-based modulation? More information can be found here. The organ-based modulation capability is particularly important if you are a younger patient or plan on living, secondary cancer free, more than 20 years after scanning. Not all organs are equally sensitive to radiation and the “organ-based modulation” feature insures lowest radiation to the most radiation-sensitive organs, i.e. breast, gonads, eyes, and thyroid.

You now have a simple way to find out if the CT scan you are about to get is giving you the lowest reasonable dose of ionizing radiation irrespective of the CT scanner brand. And, always remember: Ionizing radiation is cumulative and demands justification for its use.

Wayne Wells AKA WWW edited by Janet Morrison

About Wayne Wells

I am a 63-year-old patient diagnosed in 2006. I have no academic background and cannot give medical advice. I have, however, made an effort to study CLL/SLL and have been around the block with failed standard therapies which damaged my kidneys and led me to participate in a Phase I-b clinical trial for a drug called PCI-32765, renamed Ibrutinib or Imbruvica. This clinical trial likely saved my life and I am happy to report that I have achieved a Complete Response (CR) remission in the blood and lymph nodes. I am currently scheduled for my 12th CT scan since diagnosis with nine of those sessions occurring within the three-year period of my Ibrutinib clinical trial.